Damage from High Winds and Hail in Northern Ohio – June 25, 2013

Posted by in Weather Events | June 27, 2013

Local television news media and the Plain Dealer reported damage in Northern Ohio from a storm that passed through the area during the late afternoon and evening of June 25, 2013.  The storm was comprised of heavy rainfall, high winds, and in some areas hail.
Widespread flooding was shown in North Ridgeville.  Power outages were reported throughout the area.  Photographs of fallen tree limbs and tall trees were submitted to the local television stations by viewers from around the area.  Photographs of hail up to about 1 inch in diameter (the size of an American quarter) were submitted from Independence, Hartville, and Wooster.  The photographs submitted from Valley City showed hail about the size of an American  penny.
A review of wind records disclosed that wind gusts measured up to 62 MPH:
Cleveland Hopkins Airport – 58 MPH NW
Cleveland lakefront – 45 MPH WNW
Lorain lakefront –  62 MPH WNW
Avon – 24 MPH WNW
Belden Village – 24 MPH NNW
Kamms Corners – 24 MPH NNW
Grafton – 14 MPH NNW
The most dramatic and tragic damage was the falling of a highway sign on the Valley View bridge of I-480. Highway signs are usually designed for wind speeds of 90 MPH.  Investigations into the failure of the signs and an estimate of the wind speed on the elevated bridge at the time of the failure are not complete as of this writing.
Since the bridge is several hundred feet above the Cuyahoga Valley, it is possible that the wind pressures and the wind speed were greater on the bridge at the time of the failure than the wind speeds measured at the 33 foot height at the airport or the lower heights at other local weather stations.  Fortunately, most design standards and codes consider the height of an object when determining the wind pressures generated by the design wind,  such as 90 MPH for highway signs.  For example, an object high above the grade, such as a sign on the I-480 bridge, one may be designing for an equivalent wind speed of 110 MPH or greater.  This higher design pressure or design wind speed is due to the lack of obstructions slowing the wind at that very high height.  Just about everyone has experienced that by feeling the relatively low winds at grade compared to feeling the relatively high winds on a high balcony or an observation deck.
The results of the investigation will be interesting.  The results may have an effect on future codes and standards for the design of highway signs.